三年唔發市，發市當三年 [－－－发－－发－当－－]

Jyutping saam1 nin4 m4 faat3 si5 faat3 si5 dong3 saam1 nin4
Pinyin sān nián wú fā shì ， fā shì dāng sān nián

Definitions (粵典–words.hk)
  1. 語句、俚語
    形容​一​啲​生意​好​耐​都​賺​唔​到​錢​，​但​係​一​賺​就​會​賺​好多
    business with a very high profit margin and few transactions

三年唔發市，發市當三年 [－－－发－－发－当－－]

Jyutping saam1 nin4 m4 faat3 si5, faat3 si5 dong3 saam1 nin4
Pinyin sān nián wú fā1shi4 fā1shi dāng sān nián

Definitions (CC-CANTO)
  1. to have an unexpectedly huge upturn / win after a long period of downturn [colloquial]